The proteasome plays a pivotal role in the turnover of regulatory transduction proteins induced by activated cell membrane growth factor receptors. The epidermal growth factor receptor (EGFR) pathway is crucial in the development and progression of human epithelial cancers. The combined treatment with EGFR inhibitors has a synergistic growth inhibitory and pro-apoptotic activity in different human cancer cells which possess a functional EGFR-dependent autocrine growth pathway through to a more efficient and sustained inhibition of Akt.
EGFR inhibitors have been approved or tested for treatment of a variety of cancers, including non-small cell lung cancer (NSCLC), head and neck cancer, colorectal carcinoma, and Her2-positive breast cancer, and are increasingly being added to standard therapy. EGFR inhibitors, which may target either the intracellular tyrosine kinase domain or the extracellular domain of the EGFR target, are generally plagued by low population response rates, leading to ineffective or non-optimal chemotherapy in many instances, as well as unnecessary drug toxicity and expense. For example, a reported clinical response rate for treatment of colorectal carcinoma with cetuximab (a chimeric monoclonal antibody targeting the extracellular domain of EGFR) is about 11% (Cunningham et al, N Engl Med 2004; 351: 337-45), and a reported clinical response rate for treatment of NSCLC with erlotinib is about 8.9% (Shepherd F A, et al, N Engl J Med 2005; 353:123-132).
In particular resistance has been observed in case of KRAS mutation.
In colorectal cancer, as KRAS mutations are clearly associated with resistance to anti-EGFR antibodies (Lievre et al, Cancer Res. 2006 66(8):3992-5), one of the major challenges is to identify, in non-mutated KRAS patients, other markers that can predict lack of response to this therapy. Among them, amplification or activating mutations of oncogenes and inactivating mutations of tumor suppressor genes described above are relevant candidates, such as the level of activation of EGFR downstream signaling pathway evaluated by the measurement of EGFR downstream phosphoprotein expression.
In lung cancer, three groups of patients are emerging: one counts the patients with EGFR mutated tumors for which the use of EGFR tyrosine kinase inhibitors (EGFR TKI) was proven to improve outcome, the second counts the patients with KRAS mutated tumors for which anti-EGFR therapies are probably not the good alternatives, and the third group counts the non-EGFR and non-KRAS mutated tumors for which response cannot be predicted. No marker linked to drug response in the non-mutated tumor group has proved valuable so far.
Thus, there is a need for predicting patient responsiveness to EGFR inhibitors prior to treatment with such agents, so as to better individualize patent therapy.
There are many documents in the prior art concerning the involvement of micro RNAs (miRNAs) in sensibility or resistance to various anticancer treatments. However, in most cases, studies are partial, incomplete, and actually do not permit a true prediction of clinical response or non-response to treatment. Indeed, in many cases, studies are limited to the analysis of the expression of miRNAs in vitro, in cell lines sensitive or resistant to a particular treatment, or in tumor cells isolated from a patient tumor. In addition, in many studies, while differences in expression level between two populations of cells or patients are shown, no threshold value or score actually permitting to predict response or non-response in a new patient are provided. This is partly linked to the first shortage that many studies lack data obtained in a clinical setting. Moreover, even when some data obtained in a clinical setting is presented, these data are most of the time only retrospective, and data validating a prediction method in a new cohort are often lacking.
As an example, WO2010/121238 describes the analysis of miRNAs expression in lung cancer cell lines sensitive or resistant to EGFR tyrosine kinase inhibitors cultures in vitro. No data obtained in a clinical setting is presented.
WO2009/080437 broadly claims methods for predicting response or non-response to anticancer treatment. However, data presented in WO2009/080437 is limited to various conventional chemotherapy treatments, and no data is provided concerning EGFR inhibitors (neither for anti-EGFR monoclonal antibodies nor for EGFR tyrosine kinase inhibitors). In addition, data presented for other chemotherapeutic molecules were obtained based on expression of miRNAs in tumor cells isolated from patient's tumors cultured in vitro. No data obtained in a clinical setting is presented.
Similarly, while WO2011/135459 broadly claims methods for predicting response or non-response to anticancer treatment, data presented in this document are limited to prediction of sensitivity or resistance of cancer cell lines to various anticancer agents in vitro. Here also, no data obtained in a clinical setting is presented, and thus no correlation between miRNA expression level and clinical response or survival of patient is demonstrated.
Ragusa et al-2010 (Ragusa M. et al. Mol Cancer Ther. 2010 December; 9(12):3396-409) analyzed the expression level of miRNAs after treatment with cetuximab in colorectal cancer cell lines known to be sensitive or resistant to cetuximab treatment. Two miRNAs are shown to be differentially expressed in KRAS wild-type versus KRAS mutated patients. However, differential expression in KRAS wild-type versus KRAS mutated patients does not permit to predict response to EGFR inhibitors in KRAS wild-type patients. In addition, as in many other studies, no data obtained in a clinical setting showing the ability of the expression levels of these miRNAs to independently predict response to EGFR inhibitors in patients is presented.
Hatakeyama et al-2010 (Hatakeyama H. et al. PLoS One. 2010 Sep. 13; 5(9):e12702) discloses the comparison of proteins activated in two cell lines derived from squamous cell carcinoma of the head and neck, one sensitive and the other resistant to cetuximab, after cetuximab treatment in vitro. An EGFR ligand, (HB-EGF or TGFA) is found in higher amount in the cetuximab resistant cell line. This protein is regulated by miR-22. In this study also, no data obtained in a clinical setting showing the ability of miR-22 expression level to predict response to cetuximab in patients is presented.
Therefore many studies lack clinical data showing that the expression level of a particular miRNA actually permits to discriminate between patients that clinically respond to the treatment (resulting in increased survival) and those with progressive disease and decreased survival. While data on cell lines or tumor cells in vitro may be considered as supporting further analysis for prediction of response or non-response in a clinical setting, it is clearly not sufficient to be considered as providing a true method for prediction of clinical response in patients. This is notably demonstrated by the fact that miRNAs found to be differentially expressed in sensitive versus resistant cell lines or tumor cells in vitro in the above mentioned documents were not found to be significantly correlated to clinical response (progression free survival or overall survival) in the clinical data analyzed in the present application.
There was thus a need for true and validated methods for predicting response to EGFR inhibitors in patients for which such therapy is one of several options. The present invention provides a response to this need.